See also

Verb

A sign is an entity which signifies another
entity. A natural sign is an entity which bears a causal relation
to the signified entity, as thunder is a sign of storm. A
conventional sign signifies by agreement, as a full stop signifies
the end of a sentence. (Contrast a symbol which stands for another
thing, as a flag may be a symbol of a nation)

Any given signifier or symbol is dependent upon
that which is intended, expressed, or signified in a semiotic relationship of
signification, significance, meaning,
or import. Thus, for example, people may speak of the significance
of events, the signification of characters, the meaning of
sentences, or the import of a communication. These different
relationships that exist between sorts of signs can help people and
sorts of things that are signified can be called the modes of
signification.

The range of uses of signs are varied. They might
include: the indication or mark of something, a display of a
message, a signal to draw attention, evidence of an underlying
cause (for instance, the symptoms of a disease are signs of the
disease), a character for a mathematical operation, a body gesture,
etc.

Nature of signs

Semiotics,
epistemology,
logic, and philosophy
of language are concerned about the nature of signs, what they
are and how they signify. The nature of signs and symbols and
significations, their definition, elements, and types, is mainly
established by Aristotle,
Augustine,
and Aquinas. According
to these classic sources, significance is a relationship between
two sorts of things: signs and the kinds of things they signify
(intend, express or mean), where one term necessarily causes
something else to come to the mind. Distinguishing natural signs
and conventional signs, the traditional theory of signs sets the
following threefold partition of things:

There are things that are just things, not any sign at all;

There are things that are also signs of other things (as
natural signs of the physical world and mental signs of the mind);

There are things that are always signs, as languages (natural
and artificial) and other cultural nonverbal symbols, as documents,
money, ceremonies, and rites.

Thus there are things which may act as signs
without any respect to the human agent (the things of the external
world, all sorts of indications, evidences, symptoms, and physical
signals), there are signs which are always signs (the entities of
the mind as ideas and images, thoughts and feelings, constructs and
intentions); and there are signs that have to get their
signification (as linguistic entities and cultural symbols). So,
while natural signs serve as the source of signification, the human
mind is the agency through which signs signify naturally occurring
things, such as objects, states, qualities, quantities, events,
processes, or relationships. Human language and discourse, communication, philosophy, science, logic, mathematics, poetry, theology, and religion are only some of
fields of human study and activity where grasping the nature of
signs and symbols and patterns of signification may have a decisive
value.

Signedness, in
computing, is the property that a representation of a number has
one bit, the sign bit, which denotes whether the number is
non-negative or negative. A number is called signed if it contains
a sign bit, otherwise unsigned. See also
signed number representation

In mathematics,
the sign of a permutation tells whether it
is the product of an even or odd number of transpositions